''.split(',') is [''] which evaluates to false ...
e80b37ff was still incorrect

This was not really backward compatible with old slapos versions not passing
zserver_address_list

This was not really backward compatible when running with old slapos,
because default value was not string in this case.

/reviewed-on nexedi/erp5!742

As it is backward compatible, this option can be passed as environment
variable.

Also re-order all argument output to make it clear which comes from
SlapOS generated wrapper and which are passed by test node.

We now access zserver behind the backend apache on https:// and this
apache's certificate is not trusted

Otherwise running in debug mode on headless machines just display
cryptic error message.

/reviewed-on nexedi/erp5!705

/reviewed-on nexedi/erp5!671

1. accept a list of converison server
2. retry in case of network error

only calculate exchange rate if necessary
use transaction cache

remove useless test_21
update test_20 with various packing list

multiple owner test case
multiple cancel packing list test
circular movement test

(cherry picked from commit 27126964)

Let's use reference_date_method_id on Trade Model Paths.

* Code clean up
* Remove hardcoded ledger to pick date
* Add code to defined source section when none is defined

* Fix for special case where purchase packing list is root.

* Use getSourceAssetPriceCurrency
* Do not expand if no SourceAssetPrice